In recent years, in illumination devices, illumination light sources are progressing to replace light bulbs or fluorescent lamps with power saving and long life light sources, for example, light emitting diodes (LEDs). In addition, new illumination light sources such as, for example, Electro-Luminescence (EL) or an organic light emitting diode (OLED) are under development. Since a light output of such an illumination light source depends on the value of a flowing current, a power supply circuit supplying a constant current is necessary to light illumination. In addition, a supplied current is controlled for dimming.
For example, a dimmer of a two-wire type or like which is configured to control a phase where a triac is turned on is widespread as a dimmer of the light bulb. For this reason, an illumination light source such as an LED can be preferably dimmed with the dimmer.
However, there are cases where an output voltage of the dimmer varies due to a variation in a power supply voltage and thus flickering occurs.